A high-conductance mode of a poly-3-hydroxybutyrate/calcium/polyphosphate channel isolated from competent Escherichia coli cells

• Published in: FEBS letters 2005-09, Vol.579 (23), p.5187-5192
• Main Authors: Pavlov, Evgeny, Grimbly, Chelsey, Diao, Catherine T.M., French, Robert J.
• Format: Article
• Language: English
• Subjects: Calcium - metabolism; Calcium Channels - metabolism; E K; E rev; equilibrium potential for K; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - metabolism; Hydroxybutyrates - metabolism; Ion Channel Gating; Lanthanum - metabolism; Lipid Bilayers; Membrane Potentials; Multiprotein Complexes; Patch-Clamp Techniques; PHB; Planar lipid bilayers; poly-3-hydroxybutyrate; Polyesters - metabolism; polyP; Polyphosphate; Polyphosphates - chemistry; Polyphosphates - metabolism; Reconstitution; reversal potential
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/j.febslet.2005.08.032

Reconstitution into planar lipid bilayers of a poly-3-hydroxybutyrate/calcium/polyphosphate (PHB/Ca 2+/polyP) complex from Escherichia coli membranes yields cationic-selective, 100 pS channels (Das, S., Lengweiler, U.D., Seebach, D. and Reusch, R.N. (1997) Proof for a non-proteinaceous calcium-selective channel in Escherichia coli by total synthesis from ( R)-3-hydroxybutanoic acid and inorganic polyphosphate. Proc. Natl. Acad. Sci. USA 94, 9075–9079). Here, we report that this complex can also form larger, weakly selective pores, with a maximal conductance ranging from 250 pS to 1 nS in different experiments (symmetric 150 mM KCl). Single channels were inhibited by lanthanum (IC 50 = 42 ± 4 μM, means ± S.E.M.) with an unusually high Hill coefficient (8.4 ± 1.2). Transition to low-conductance states (250 pS) may reflect conformations important for genetic transformability, or “competence”, of the bacterial cells, which requires the presence of the PHB/Ca 2+/polyP complex in the membrane.